function cluster_member_n, clusters,n
  dims = SIZE(clusters, /DIMENSIONS)
  num = dims[1] + 1L
  n>=1
  work = lindgen(num)
  for i=0L, num-1L-n do $
     work[where(work eq clusters[0,i] OR work eq clusters[1,i])]= num+i
  return, work
end 